Thermoacoustic instability: Model-based optimal control designs and experimental validation

Active control of thermoacoustic instability has been increasingly sought a fter in the past two decades to suppress pressure oscillations while mainta ining other performance objectives such as low NOx emission, high efficienc y, and power density. Recently, we have developed a feedback model of a pre mixed laminar combustor which captures several dominant features in the com bustion process such as heat release dynamics, multiple acoustic modes, and actuator effects. In this paper, we study the performance of optimal contr ol designs including LQG-LTR and H-infinity methods using the model with ad ditional effects of mean heat and mean flow, actuator dynamics, and input s aturation. We also verify these designs experimentally using a 1 kW bench-t op combustor rig and a 0.2-W loudspeaker over a range of flow rates and equ ivalence ratios. Our results show that the proposed controllers, which are designed using a two-mode finite dimensional model, suppress the thermoacou stic instability significantly faster than those obtained using empirical a pproaches in similar experimental setups without creating secondary resonan ces, and guarantee stability robustness.